In processes for high-volume production of glass articles such as plate glass, a glass material is heated to produce molten glass, and the molten glass so produced is molded to manufacture glass articles such as plate glass. If the molten glass is heterogeneous, striae may form in the glass articles.
Striae are zones of striated appearance differing in refractive index and/or specific gravity from the surrounding area; in optical components such as lenses, substrates for liquid crystal displays (LCD), and other such applications, there is a need to rigorously eliminate them from the glass articles. Stirring of the molten glass by a stirring device is performed in order to prevent striae. A typical stirring device is provided with a chamber of round cylindrical shape, and a stirrer. The stirrer has a shaft serving as a rotation axis, and blades connected to the side wall of the shaft. In the stirring device, molten glass is supplied into a chamber in which the stirrer is disposed, and the molten glass is stirred by axially rotating blades, rendering the molten glass homogeneous.
Patent Document 1 (Japanese Unexamined Patent Application Publication 2001-72426) discloses a stirring device for molten glass, provided with a stirrer having a shaft serving as a rotation axis, and blades connected to the side wall of the shaft. In this stirring device, because the stirrer is arranged in a state in which some of the blades are in proximity to the inner wall of the stirred tank, the molten glass can be homogeneously stirred.
Patent Document 2 (Japanese Unexamined Patent Application Publication 2007-204357) discloses a stirring device for molten glass, in which higher stirring effect can be achieved by connecting a plurality of stirring devices.